More than a third of Americans regularly sleep less than seven hours a night, affecting their ability to concentrate, according to the Centers for Disease Control and Prevention.

Short sleep duration was found among 35 percent of adults surveyed, and 48 percent reported snoring, an unhealthy behavior, according to a study in the journal Morbidity and Mortality Weekly Report Thursday. About 39 percent of respondents aged 25 to 54 reported sleeping less than 7 hours in a day.

The most common side effect of sleep-related difficulties was loss of concentration, followed by trouble remembering, another report found. Most adults need seven to nine hours of slumber to avoid higher likelihood of illness and death, the Washington-based National Sleep Foundation said.

“Poor sleep habits, which include not scheduling enough time for sleep, can be assessed during general medical care visits and improved with effective behavioral changes,” the authors wrote in an editorial following the study by the Atlanta-based CDC.

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The duration study is the first to examine prevalence of unhealthy sleep behaviors, the authors wrote. The second report is the first investigation of a link between shortened sleep and related difficulties in a non-clinical setting, the authors wrote.

Health-care providers can help patients by advising them to keep a regular schedule and to sleep in a dark place with a controlled temperature, the report’s authors wrote. People with sleep disorders should avoid caffeine, alcohol, nicotine, and strenuous exercise in the evening. Full or empty stomachs at bedtime can also make sleeping more difficult.

The process included interviews for data on sleep duration with a total of 74,571 people in California, Georgia, Hawaii, Illinois, Kansas, Louisiana, Maryland, Minnesota, Nebraska, New York, Texas and Wyoming.

The report investigating the link between less slumber and related difficulties involved 10,000 participants. The study combined data from 2005-2006 and 2007-2008 surveys, the authors wrote.